Get Best Civil Engineering Knowledge YouTube
Home
Bridge Engineering

Bridge Engineering

HISTORY OF BRIDGE DEVELOPMENT

  • The bridge is one of the oldest instruments of our civilization. In prehistoric times the first bridges were made by spanning the small streams with the help of fallen trees or logs of wood. 
  • Later, suspension-type bridges were made by twisted creepers tied to tree trunks on either side of a gorge. These primitive efforts were followed by the lintel bridge consisting of a large piece of stone resting on two or more small pieces of stone; then the timber bridge such as were used in medieval times and then stone and metal bridges. 
  • According to Degrand, the earliest bridge on record is that built on the Niles by Menes the first king of Egypt in about 2650 B.C. but no details are known about this. Diodorus Siculus has given a detailed description of a wooden bridge built by the queen of Babylon Semirawis over the Euphrates river in the year 783 B.C. This bridge had detachable wooden platforms supported on stone piers. These wooden platforms were used to be removed during nights to prevent thieves from entering the city.
  • In ancient India - the period of Ramayana construction of bridges was well known. Even today the portion of the sea where the bridge was built is popularly known as 'Setu Samudra'.
Bridge Engineer


COMPONENTS OF A BRIDGE

  • Broadly a bridge can be divided into two major parts: (i) Superstructure, (11) Substructure.
  • The superstructure of a bridge is analogous to a single-story building roof and substructure to that of walls, columns, and foundations supporting it.
  • The superstructure consists of structural members carrying a communication route. Thus, handrails, guard stones, and flooring supported by any structural system such as beams, girders, arches, and cables above the level of bearings constitute the superstructure.

The substructure is a supporting system for the superstructure. It consists of the following:

(i) Abutments, (ii) Piers and Abutment piers, (iii) Wing walls, and (iv) Foundations for the piers and abutments.

The other main parts of bridge structure are approaches, bearings, and river training works, like aprons, revetment for slopes at abutments, etc.

SOME DEFINITIONS

The following definitions of certain important terms used in bridge engineering are given below:

1. Bridge: A structure facilitating a communication route for carrying road traffic or other moving loads over a depression or obstruction such as river, stream, channel, road or railway. The communication route may be a railway track, a tramway, a roadway, a footpath, a cycle track, or a combination of them.

2. High-Level Bridge or Non-submersible Bridge: The bridge which does not allow the high floodwaters to pass over them. All the flood water is allowed to pass through its vents. In other words, it carries the roadway above the highest flood level of the channel.

3. Submersible Bridge: A submersible bridge is a structure that allows floodwater to pass over a bridge submerging the communication route. Its formation level should be so fixed as not to cause interruption to traffic during floods for more than three days at a time nor for more than six times a year.

4. Causeway: It is a pucca submersible bridge that allows floods to pass over it. It is provided on less important routes in order to reduce the construction cost of cross drainage structures. It may have vents for low water flow.

5. Foot Bridge: The footbridge is a bridge exclusively used for carrying pedestrians, cycles and animals.

6. Culvert: When a small stream crosses a road with a linear waterway less than about 6 metres, the cross drainage structure so provided is called a culvert.

7. Deck Bridges: These are the bridges whose floorings are supported at top of the superstructures.

8. Through Bridges: These are the bridges whose floorings are supported or suspended at the bottom of the superstructures.

9. Semi-Through Bridges: These are the bridges whose floorings are supported at some intermediate level of the superstructure. 

10. Simple Bridges: They include all beam, girder or truss bridges supported at both ends only. It is suitable for spans up to 8 metres. 

11. Cantilever Bridges: Bridges that are more or less fixed at one end and free at the other. It can be used for spans varying from 8 metres to 20 metres.


Post a Comment